Secure Multicast/Broadcast Ranging

ABSTRACT

Methods performed by a first device. The methods include transmitting a first ranging poll to a plurality of second devices, receiving a polling response message from each of at least a first subset of the second devices, determining a propagation delay for each of the received polling response messages and determining a distance to each of the first subset of the second devices based on at least the respective propagation delays. The methods further include receiving a ranging poll from a second device, wherein the ranging poll is one of a multicast transmission or a broadcast transmission, determining a type of response to be transmitted to the second device based on at least a capability of the first device and transmitting a response of the determined type to the second device.

BACKGROUND INFORMATION

The IEEE 802.15.4 standard specifies a physical layer (PHY) and a mediaaccess control (MAC) layer for operation of low-rate WPANs (LR-WPANs).These types of networks are typically referred to as Ultra-Wideband(UWB) networks. UWB networks may connect wireless electronic devices invarious arrangements. In one example, a UWB network may comprise aprimary device and one or more secondary devices. The devices of the UWBnetwork may perform various functionalities with respect to the otherdevices connected to the UWB network.

SUMMARY

Exemplary embodiments include a method performed by a first device. Themethod includes receiving a ranging poll from a second device, whereinthe ranging poll is one of a multicast transmission or a broadcasttransmission, determining a type of response to be transmitted to thesecond device based on at least a capability of the first device andtransmitting a response of the determined type to the second device.

Further exemplary embodiments include a device having a transceiver anda processor. The transceiver is configured to transmit a first rangingpoll to a plurality of second devices and receive a polling responsemessage from at least a first subset of the second devices. Theprocessor is configured to determine a propagation delay for each of thereceived polling response messages and determine a distance to each ofthe first subset of the second devices based on at least the respectivepropagation delays.

Still further exemplary embodiments include a method performed by afirst device. The method includes receiving a ranging poll from a seconddevice, wherein the ranging poll is one of a multicast transmission or abroadcast transmission, determining a type of response to be transmittedto the second device based on at least a capability of the first deviceand transmitting a response of the determined type to the second device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary network arrangement according to variousexemplary embodiments.

FIG. 2 shows an exemplary wireless device according to various exemplaryembodiments.

FIG. 3 shows a first exemplary timing diagram for a broadcast rangingoperation according to various exemplary embodiments.

FIG. 4 shows a second exemplary timing diagram for a multicast rangingoperation according to various exemplary embodiments.

FIG. 5 shows an exemplary MAC Information Element (IE) according tovarious exemplary embodiments.

DETAILED DESCRIPTION

The exemplary embodiments may be further understood with reference tothe following description and the related appended drawings, whereinlike elements are provided with the same reference numerals. Theexemplary embodiments are related to a system and method for performinga secure broadcast or multicast ranging procedure in a UWB network. Itmay be desirable for a primary device in a wireless personal areanetwork (WPAN) to determine a distance to one or more secondary devices.The exemplary embodiments describe a ranging procedure that allows theprimary device to avoid an individual ranging procedure for each of thesecondary devices, thereby decreasing a number of packets exchanged inthe UWB network during ranging operations.

The exemplary embodiments are described with respect to devices that mayoperate according to the IEEE 802.15.4 standard. However, it should beunderstood that the exemplary embodiments of the ranging operation maybe used by devices using any UWB protocol. In addition, the termswireless personal area network (WPAN) and Ultra-Wideband (UWB) networkare used interchangeably throughout this description and those skilledin the art will understand the general characteristics of such networks.

FIG. 1 shows an exemplary network arrangement 100 according to variousexemplary embodiments. The exemplary network arrangement 100 includes aprimary device 105 and a plurality of secondary devices 110-130. Theprimary device 105 and the secondary devices 110-130 may be any type ofelectronic component that is configured to operate within a UWB network,e.g., mobile phones, tablet computers, smartphones, phablets, embeddeddevices, wearable devices, Cat-M devices, Cat-M1 devices, MTC devices,eMTC devices, other types of Internet of Things (IoT) devices, accesspoints, etc. It should be understood that an actual network arrangementmay include any number of secondary devices. The example of fivesecondary devices 110-130 is only provided for illustrative purposes. Itshould also be understood that any of the devices 105-130 may bedesignated a primary device and similarly, any of the devices 105-130may be designated as a secondary device for a particular rangingoperation. That is, the device that initiates the ranging operation maybe designated as the primary device.

The primary device 105 and the secondary devices 110-130 may beconfigured to communicate over the UWB network. However, it should beunderstood that the primary device 105 and the secondary devices 110-130may also communicate with other types of wireless networks (cellular ornon-cellular) and may also communicate using a wired connection. Withregard to the exemplary embodiments, the primary device 105 and thesecondary devices 110-130 may communicate over the UWB network to, amongother functionalities, transmit or receive data.

FIG. 2 shows an exemplary wireless device 105 according to variousexemplary embodiments. It should be understood that the exemplarywireless device 105 of FIG. 2 may also represent any of the otherwireless device 110-130 of the network arrangement 100. The wirelessdevice 105 may include a processor 205, a memory arrangement 210, adisplay device 215, an input/out (I/O) 220, a transceiver 225, and othercomponents 230. The other components 230 may include, for example, anantenna, an audio input device, an audio output device, a battery, adata acquisition device, ports to electrically connect to otherelectronic devices, etc.

The processor 205 may be configured to execute a plurality ofapplications of the device 105. In one exemplary embodiment, anapplication may include a ranging application 235 as will be describedin greater detail below. The described functionalities of the wirelessdevice 105 being represented as an application (e.g., a program)executed by the processor 205 is only exemplary. The functionalityassociated with the applications may also be implemented as a separateincorporated component of the wireless device 105 or may be a modularcomponent coupled to the wireless device 105, e.g., an integratedcircuit with or without firmware. In addition, in some wireless devices,the functionality described for the processor 205 is split among twoprocessors, a baseband processor and an application processor. Theexemplary embodiments may be implemented in any of these or otherconfigurations of a wireless device.

The transceiver 225 may be a hardware component configured to transmitand/or receive data. For example, the transceiver 225 may enablecommunication with other electronic devices directly or indirectlythrough one or more networks based upon a protocol and an operatingfrequency of the network. The transceiver 225 may operate on a varietyof different frequencies or channels (e.g., set of consecutivefrequencies). Thus, one or more antennas (not shown) coupled with thetransceiver 225 may enable the transceiver 225 to communicate with otherwireless devices (e.g., wireless devices 110-130) via a UWB network.

The exemplary embodiments describe the primary device 105 determining adistance to and/or a location of each of the plurality of secondarydevices 110-130 using a ranging operation. Throughout this description,the term “distance” will be used to refer to the distance betweendevices and/or the location of the secondary device 110-130 eitherrelative to the primary device 105 or an absolute location within aparticular space. Three exemplary ranging modes are described. A singlenode ranging mode is utilized for determining a distance to a singlesecondary device, e.g. secondary device 110. A multicast ranging mode isutilized for determining a distance to a plurality of secondary devices,e.g. secondary devices 110-130, when the number and identity of thesecondary devices 110-130 are known to the primary device 105. Forexample, in the network arrangement 100, the number of secondary devicesis five. The identity of the secondary devices 110-130 may be known tothe primary device 105 through any number of manners, e.g. previous dataexchanges, previous ranging operations, etc. A broadcast ranging mode isutilized for determining a distance to a plurality of secondary devices,e.g. secondary devices 110-130, when the number of secondary devices andthe identity of each of the secondary devices are not known to theprimary device 105. However, even when the identities of the secondarydevices 110-130 are not known to the primary device 105, the devices105-130 may share a common key that may be used to receivestation-to-station messages. For example, keys may be shared via anupper layer protocol either over the UWB network or a sideband channel.

The ranging application 235 may implement one or more of these rangingmodes. In the below description, the operation of the exemplarymulticast ranging mode and broadcast ranging mode will be described indetail. The single node ranging mode operation will not be described asthat mode will operate in accordance with conventional rangingoperations.

FIG. 3 shows a first exemplary timing diagram for a broadcast rangingoperation 300 according to various exemplary embodiments. The broadcastranging operation 300 will be described with reference to the networkarrangement 100 of FIG. 1 . As shown in FIG. 3 , one exemplary ranginground 350 is illustrated. As will be described in greater detail below,there may be multiple rounds of ranging operations performed.

In the ranging round 350, the primary device 105 may transmit a pre-pollmessage 305 that includes ranging configuration information for thesecondary devices 110-130. The pre-poll message 305 is not required tobe transmitted in every ranging round. For example, the ranging round350 may be a subsequent ranging round and a previous pre-poll messageincluding the configuration information may have been sent by theprimary device 105 and received by the secondary devices 110-130. Thus,the same configuration information is not required to be sent multipletimes. In one example, the ranging configuration information may remainvalid until a next pre-poll message is transmitted. In another example,the configuration information may be included in the ranging poll 210(described below). In a further example, the configuration informationmay be included in other messages exchanged between the wireless devices105-130, either via the UWB network or another network/protocol. In anycase, the secondary devices 110-130 connected via the UWB network willreceive the ranging configuration information.

The primary device 105 may then broadcast a first ranging poll 310 tothe secondary devices 110-130 via the UWB network. The first rangingpoll 310 may include various information allowing the secondary devices110-130 to respond to the poll. This information of the first rangingpoll 310 may be included in a MAC information element (IE) 500, as willbe described in further detail with respect to FIG. 5 .

The secondary devices 110-130 may contend for available polling responseslots and respond to the first ranging poll 310 by transmitting pollingresponse messages 315 a-c to the primary device 105. The pollingresponse slots are indicated as R₁, R₂ . . . R_(N), wherein N is anumber of available slots. As will be described below, the number ofavailable slots N may be configurable by the primary device 105.

After receipt of the polling response messages 315 a-c by the primarydevice 105, it may be considered that the ranging round 350 is complete.For example, the primary device 105 may have received sufficientinformation in the polling response messages 315 a-c to determine thedistance to the secondary devices 110-130. However, a second rangingpoll 320 of the same ranging round 350 may also be used. For example, ifprecise ranging with clock drift cancellation is used, the secondranging poll 320 and corresponding responses (described below) may beused. In another example, when a time stamp is not included in thepolling response messages 315 a-c, the primary device 105 may not beable to derive the propagation delay inherent in sending messages acrossa distance. For example, if the precise timing is known for thetransmission of the polling response message by one of the secondarydevices 110-130 and for the reception of the polling response message bythe primary device 105, then the primary device 105 can derive thedistance between the devices. Thus, when any one of the secondarydevices 110-130 is not capable of including time stamps in the pollingresponse messages 315 a-c, the second ranging poll 320 may be used.

When the second ranging poll 320 is used, the primary device 105broadcasts a second ranging poll 320 to the secondary devices 110-130via the UWB network. The second ranging poll 320 may be substantiallysimilar to the first ranging poll 310, with appropriate modifications tothe MAC IE 400 to indicate the expected response is a timestampresponse.

The secondary devices 110-130 may then contend for available time stampreporting slots and respond to the second ranging poll 320 bytransmitting time stamp response messages 325 a-c to the primary device105. Alternatively, the secondary devices 110-130 may occupy the sameslot as used to transmit the polling response messages 315 a-c. Itshould be understood that the same slot means the same slot after therespective poll. For example, if the secondary device 110 transmittedpolling response message 315 a in slot R₁ after ranging poll 310, thesecondary device 110 will transmit time stamp response message 325 a inslot T₁. The timing response slots are indicated as T₁, T₂ . . . T_(N),wherein N is the number of available slots. The time stamp responsemessages 325 a-c may each include a time stamp. The primary device 105may use the respective time stamps to derive a distance between theprimary device 105 and each of the plurality of secondary devices110-130.

The primary device 105 may also transmit a message 330 comprising timestamps to the secondary devices 110-130. The primary device 105 mayreport its time stamps to allow the secondary devices 110-130 toindependently derive the distance between the devices. Thus, aftermessage 330 is transmitted, the ranging round 350 is complete.

FIG. 4 shows a second exemplary timing diagram for a multicast rangingoperation 400 according to various exemplary embodiments. The multicastranging operation 400 will be described with reference to the networkarrangement 100 of FIG. 1 . Again, the timing diagram of FIG. 4 willillustrate a single ranging round 450, but multiple rounds are possible.

The primary device 105 may transmit a pre-poll message 405 carryingranging configuration information to the secondary devices 110-130 viathe UWB network. The transmission of the pre-poll message 405 may besubstantially similar to the transmission of the pre-poll message 305.

The primary device 105 may multicast a first ranging poll 410 to thesecondary devices 110-130. The first ranging poll 310 may besubstantially similar to the first ranging poll 310, with appropriatefield adjustments to indicate multicast ranging, as will be described infurther detail with respect to FIG. 5 .

The secondary devices 110-130 may be scheduled to transmit pollingresponse messages 415 a-c in a polling response slot. The pollingresponse slots are indicated as R₁, R₂ . . . R_(N), wherein N is anumber of available slots. The polling response slot for each secondarydevice 110-130 may be scheduled by the primary device 105 because thenumber and identities of the secondary devices are known to the primarydevice 105. However, in another exemplary embodiment, the secondarydevices 110-130 may contend for the polling response slots if noschedule is provided by the primary device 105.

Similar to the broadcast ranging operation 300 described with respect toFIG. 3 , receipt of the polling response messages 415 a-c may beconsidered to complete the ranging round 450. However, for substantiallysimilar reasons as described above, a second ranging poll 420 may alsobe used.

The primary device 105 may multicast a second ranging poll 420 to thesecondary devices 110-130 via the UWB network. The second ranging poll420 may be substantially similar to the first ranging poll 410, withappropriate modifications to the MAC IE 400 to indicate the expectedresponse is a timestamp response.

The secondary devices 110-130 may be scheduled to send time stampresponse messages 425 a-c in a time stamp report slot by the primarydevice 105. The time stamp report slot may be the same for a givensecondary device as the poll response slot or may be a different slot.The time stamp report slots are indicated as T₁, T₂ . . . T_(N), whereinN is the number of available slots. The time stamp response messages 425a-c each include a time stamp. The primary device 105 may use therespective time stamps to derive a distance between the primary device105 and each of the plurality of secondary devices 110-130.

The primary device 105 may also transmit a message 430 comprising timestamps to the secondary devices 110-130. The primary device 105 mayreport its time stamps to allow the secondary devices 110-130 toindependently derive the distance between the devices. Thus, aftermessage 430 is sent, the ranging round 450 is complete.

As described above, FIGS. 3 and 4 illustrate a single ranging round 350,450, respectively. The ranging rounds may be repeated as necessary. Forexample, there may be a second ranging round and a third ranging roundafter a first ranging round. The ranging rounds do not need to becontiguous, e.g., there may be time gaps between ranging rounds. Thetime gap may be indicated in the MAC IE 500. With respect to themulticast ranging operation 400, the manner of sending polling responsemessages 415 a-c, e.g., schedule-based or contention-based, may changefrom round to round.

In a further exemplary embodiment, the initial polling message maycomprise two polling messages, wherein polling message P1 may be used bya first subset of the secondary devices 110-130 and a polling message P2that may be used by a second subset, e.g. the remainder of the secondarydevices 110-130. The first and second subsets may be determined based onan ability of a secondary device to transmit time stamps in the pollingresponse message. As described above, the primary device 105 and thesecondary devices 110-130 may exchange information about rangingcapabilities. For example, if a secondary device has the capability ofsending timestamp information in a polling response message, thesecondary device may treat the ranging poll similar to the ranging polls310 and 410 and respond with a polling response message similar topolling response messages 315, 415. On the other hand, if a secondarydevice does not have the capability of sending timestamp information ina polling response message, the secondary device may treat the rangingpoll similar to the ranging polls 320 and 420 and respond with atimestamp response message similar to time stamp response message 325,425.

FIG. 5 shows an exemplary MAC IE 500 according to various exemplaryembodiments described herein. The MAC IE 500 defines various MAC fieldsto support the broadcast/multicast ranging operations described herein.For example, the MAC IE 500 may indicate the ranging mode as one of thesingle node ranging mode, the multicast ranging mode, or the broadcastranging mode. The MAC IE 500 may further indicate a number of rangingrounds, a duration of each ranging round, and a number of available pollresponse slots. The number of poll response slots may be configurable bythe primary device 105. For example, in the multicast mode where theprimary device 105 is aware of the number of secondary devices 110-130,the primary device 105 may set the number of response slots based on thenumber of secondary devices, e.g., 5 slots when there are 5 secondarydevices. The MAC IE 500 may also include a counter showing the number ofthe current exchange round (e.g. 3 of 5). If the ranging rounds arenon-continuous (e.g. there is a time gap between rounds), the MAC IE 500may point to a timing of a next poll (or pre-poll).

If the ranging mode is the multicast ranging mode, the MAC IE 500 mayspecify whether the secondary devices 110-130 are scheduled for pollresponse slots or will contend for poll response slots. If the secondarydevices 110-130 are scheduled, the MAC IE 500 may also specify the slotassignments for each of the secondary devices 110-130. However, thisspecification may also be indicated as part of the upper layerprotocols. If the ranging mode is broadcast ranging, the MAC IE 500 mayspecify a maximum number of attempts for each of the secondary devices110-130 to contend for a response slot.

As described above, the secondary devices 110-130 may contend forresponse slots. Legacy channel contention typically uses energydetection and preamble detection to sense a transmission medium prior toattempting a transmission. When a device senses that the transmissionmedium is in use, it will back off for a random time before sensing themedium again and attempting the transmission. Energy detection istypically not useful for UWB networks because UWB signals aretransmitted at a very low power over a large bandwidth. In addition,IEEE 802.15.4 specifies that different UWB packets may use differentpreambles. Thus, sensing the transmission medium by preamble detectionmay be inefficient, considering that every possible preamble would haveto be tested by the device.

In the exemplary embodiments, the process by which the secondary devices110-130 contend for the available polling response slots may beconfigurable. For example, a persistent channel use operation utilizinga free slot counter (FSC) may be used. The device may start the FSC atzero. A contending device may send a UWB packet over a channel using aspecific slot. For each UWB packet that is transmitted successfully, thedevice may increase the FSC, e.g., by one increment. For each UWB packetthat is transmitted unsuccessfully, the device may decrease the FSC,e.g., by one increment. The device may continue to use the channel/slotin this manner as long as the FSC remains at zero or above. However, ifthe FSC goes below zero, the device will deem the channel/slot to bebusy and will move to a different channel/slot.

The increment by which the FSC is increased or decreased may be afunction of a number of consecutive attempts. For example, the FSC maybe decreased by one after a first failed transmission. If the nexttransmission attempt also fails, the FSC may be decreased by 2, etc. Inthis manner, a device that has established a good connection in a givenchannel/slot will continue to use the same channel/slot, and a devicethat attempts to use the same channel/slot will move to a differentchannel/slot. This exemplary contention procedure is not limited to theexemplary ranging operations but may be applied to any scenario wheredevices are contending for transmission resources.

As described above, the exemplary embodiments are described withreference to devices that may operate according to the IEEE 802.15.4standard for UWB networks. Thus, the exemplary MAC IE 500 may be avariation of a MAC IE according to this protocol. However, if the UWBnetwork is operating using a different protocol, a MAC IE havingdifferent fields may be used to convey the information that is used forthe above described ranging operations. In addition, the informationthat is used for the ranging operation may be communicated between thedevices using information elements (or other data elements) of otherlayers.

It is well understood that the use of personally identifiableinformation should follow privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining the privacy of users. In particular,personally identifiable information data should be managed and handledso as to minimize risks of unintentional or unauthorized access or use,and the nature of authorized use should be clearly indicated to users.

It will be apparent to those skilled in the art that variousmodifications may be made to the present disclosure, without departingfrom the spirit or the scope of the exemplary embodiments. Thus, it isintended that the present disclosure cover modifications and variationsof the exemplary embodiments provided they come within the scope of theappended claims and their equivalent.

1-14. (canceled)
 15. A method, comprising: at a first device: receivinga ranging poll from a second device, wherein the ranging poll is one ofa multicast transmission or a broadcast transmission; determining a typeof response to be transmitted to the second device based on at least acapability of the first device; and transmitting a response of thedetermined type to the second device.
 16. The method of claim 15,wherein, when the first device has a capability of including a timestamp in a ranging poll response, the response is a ranging pollresponse including the time stamp.
 17. The method of claim 15, wherein,when the first device does not have the capability of including a timestamp in a ranging poll response, the response is a time stamp response.18. The method of claim 15, wherein the first device, the second deviceand at least one other device are communicatively coupled via anultra-wideband (UWB) network, the method further comprising: contendingwith the at least one other device for a slot to transmit the response.19. The method of claim 15, wherein the ranging poll includes a scheduleto transmit the response.
 20. The method of claim 15, furthercomprising: receiving a time stamp message from the second device; anddetermining a distance to the second device based on at least the timestamp message.
 21. The method of claim 15, further comprising: receivinga pre-poll message including ranging configuration information from thesecond device.
 22. The method of claim 15, wherein the ranging pollmessage includes at least one of an identification of a type of rangingoperation, a number of ranging rounds to be performed, a duration of aranging round, a number of response slots, a ranging round counter, apointer to a next ranging poll, an indication of whether the pollingresponse messages are scheduled, a slot assignment for the pollingresponse messages or a maximum number of attempts for each pollingresponse message.
 23. The method of claim 15, wherein the ranging pollcomprises the broadcast transmission, wherein the first device and thesecond device share a common key to exchange station-to-stationmessages.
 24. A first device, comprising: a transceiver configured tocommunicate with a second device; and a processor communicativelycoupled to the transceiver and configured to: receive a ranging pollfrom the second device, wherein the ranging poll is one of a multicasttransmission or a broadcast transmission; determine a type of responseto be transmitted to the second device based on at least a capability ofthe first device; and transmit a response of the determined type to thesecond device.
 25. The first device of claim 24, wherein, when the firstdevice has a capability of including a time stamp in a ranging pollresponse, the response is a ranging poll response including the timestamp.
 26. The first device of claim 24, wherein, when the first devicedoes not have the capability of including a time stamp in a ranging pollresponse, the response is a time stamp response.
 27. The first device ofclaim 24, wherein the first device, the second device and at least oneother device are communicatively coupled via an ultra-wideband (UWB)network, wherein the processor is further configured to: contend withthe at least one other device for a slot to transmit the response. 28.The first device of claim 24, wherein the ranging poll includes aschedule to transmit the response.
 29. The first device of claim 24,wherein the processor is further configured to: receive a time stampmessage from the second device; and determine a distance to the seconddevice based on at least the time stamp message.
 30. The first device ofclaim 24, wherein the processor is further configured to: receive apre-poll message including ranging configuration information from thesecond device.
 31. The first device of claim 24, wherein the rangingpoll message includes at least one of an identification of a type ofranging operation, a number of ranging rounds to be performed, aduration of a ranging round, a number of response slots, a ranging roundcounter, a pointer to a next ranging poll, an indication of whether thepolling response messages are scheduled, a slot assignment for thepolling response messages or a maximum number of attempts for eachpolling response message.
 32. The first device of claim 24, wherein theranging poll comprises the broadcast transmission, wherein the firstdevice and the second device share a common key to exchangestation-to-station messages.
 33. A processor of a first deviceconfigured to: receive a ranging poll from a second device, wherein theranging poll is one of a multicast transmission or a broadcasttransmission; determine a type of response to be transmitted to thesecond device based on at least a capability of the first device; andtransmit a response of the determined type to the second device.
 34. Theprocessor of claim 33, further configured to: receive a time stampmessage from the second device; and determine a distance to the seconddevice based on at least the time stamp message.